// The MIT License (MIT)
//
// Copyright (c) 2022 Firebase
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
const RESET_VALUE_TAG = Symbol.for("firebase-functions:ResetValue:Tag");

/**
 * Special configuration type to reset configuration to platform default.
 *
 * @alpha
 */
export class ResetValue {
  /**
   * Handle the "Dual-Package Hazard".
   *
   * We implement custom `Symbol.hasInstance` to so CJS/ESM ResetValue instances
   * are recognized as the same type.
   */
  static [Symbol.hasInstance](instance: unknown): boolean {
    return (instance as { [RESET_VALUE_TAG]?: boolean })?.[RESET_VALUE_TAG] === true;
  }

  get [RESET_VALUE_TAG](): boolean {
    return true;
  }
  toJSON(): null {
    return null;
  }
  // eslint-disable-next-line @typescript-eslint/no-empty-function
  private constructor() {}
  public static getInstance() {
    return new ResetValue();
  }
}

/**
 * Special configuration value to reset configuration to platform default.
 */
export const RESET_VALUE = ResetValue.getInstance();

/**
 * @internal
 */
export type ResettableKeys<T> = Required<{
  [K in keyof T as [ResetValue] extends [T[K]] ? K : never]: null;
}>;
